Parallel changes in red blood cell and renal Na-K-ATPase activity in adrenal and electrolyte disorders in the rat

To compare the activity of Na-K-ATPase in the red blood cells (RBCs) and in renal tissue in disorders of Na+ metabolism, the following groups of rats were studied: 1) control, intact rats, 2) adrenalectomized (ADX) rats, 3) intact rats treated with DOCA, 4) ADX DOCA-treated rats, 5) intact salt-loaded rats, 6) ADX salt-loaded rats, 7) intact dexamethasone-treated rats (DEXA), and 8) ADX DEXA-treated rats. After adrenalectomy (group 2) serum Na+ decreased and serum K+ increased. Renal Na-K-ATPase in cortex, medulla and papilla of the control group was 44 +/- 2.7 mumol Pi/mg prot/h, 128.2 +/- 5.9 and 44 +/- 3.2 respectively and in group 2 the enzyme activity was 32.5 +/- 2.0 (P less than 0.005), 81.7 +/- 4.5 (P less than 0.001) and 23.6 +/- 1.9 (P less than 0.001) respectively. RBCs Na-K-ATPase of control animals was 2.82 +/- 0.19 mumol Pi/mg prot/h, while in group 2 the activity was 1.43 +/- 0.24 (P less than 0.001). DOCA treatment of ADX rats (group 4) normalized serum electrolytes and Na-K-ATPase activity in the renal cortex and papilla and in the RBCs. In the renal medulla the correction by DOCA was only partial. Salt loading of ADX rats (group 6) normalized serum electrolytes and Na-K-ATPase activity in the renal medulla and RBCs. Salt loading of normal rats increased RBC Na-K-ATPase to 3.72 +/- 0.36 (P less than 0.02) and medullary Na-K-ATPase to 185.6 +/- 9.8 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)